In situ preparation of mixed anhydrides containing the trifluoroacetyl moiety. Application to the esterification of cholesterol and phenol

Abstract

This paper reports an easy characterization of carboxylic-trifluoroacetic mixed anhydrides by 1 H and 13 C NMR, and gives evidence that mixed anhydrides are produced instantaneously, at room temperature, from a carboxylic acid and trifluoroacetic anhydride and even from carboxylic anhydrides and trifluoroacetic acid. The esterification of phenol with the carboxylictrifluoroacetic anhydrides is highly chemoselective, and affords pure products, in quantitative yields, and in the case of cholesterol, some cholesteryl trifluoroacetate is also produced.

Ionic Liquid Based Separations of Trivalent Lanthanide and Actinide Ions.

“…Rapid nucleophilic substitution has been reported for anhydrides of carboxylic acids and trifluoroacetic acid . Section 3S and Tables 2S-11S of the Supporting Information present abundant NMR evidence for the formation of such conjugates for various acids, including trifluoroacetic acid, Hbet + , and HDEHP.…”

“…Rapid nucleophilic substitution has been reported for anhydrides of carboxylic acids and trifluoroacetic acid. 58 Section 3S and Tables 2S-11S of the Supporting Information present abundant NMR evidence for the formation of such conjugates for various acids, including trifluoroacetic acid, Hbet + , and HDEHP. We stress that reaction 6 is an equilibrium reaction that is shifted to the right for Hbet + and trifluoroacetic acid, whereas the HDEHP conjugates are considerably less stable, which is also suggested by calculations (SI Table 7S).…”

Generation of Mixed Anhydrides via Oxidative Fragmentation of Tertiary Cyclopropanols with Phenyliodine(III) Dicarboxylates

“…Thus, benzyl ester 20 was obtained in 92% yield by acylation of benzyl alcohol in the presence of Et 3 N. Acylation of phenol and pentafluorophenol can also be performed, to afford the corresponding ester products 22 and 23 . Ester 22 can also be prepared without a basic additive, upon the reaction of mixed TFA anhydride with phenol [ 65 ]. Thioester 24 was obtained in 64% yield by acylation of the corresponding thiol.…”

“…Method B [ 65 ]: A solution of phenol (47 mg, 0.5 mmol, 1.0 equiv.) in CHCl 3 (0.5 mL) was added to the solution of mixed TFA anhydride, generated from cyclopropanol 1a and reagent 2b (PIFA) in CHCl 3 .…”

Atmospheric sink of methyl chlorodifluoroacetate and ethyl chlorodifluoroacetate: temperature dependent rate coefficients, product distribution of their reactions with Cl atoms and CF2ClC(O)OH formation

“…The small carbonyl band splitting is expected for anhydrides of structure RC(O)OCHO. 34 In the ngerprint region of the product spectrum band maxima occur at $1279, $1193, $1115, $999, $966 cm À1 whereby those at 1115 and 966 cm À1 are the strongest and equally intense. Interpretation of anhydride spectra in the ngerprint region is complicated because of a large number of C-O and C-C stretchings and various bending modes, many of which are strongly mixed.…”